LIQUID-PHASE PHOTOIONIZATION DETECTOR FOR LIQUID CHROMATOGRAPHY (HPLC).
Item
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Title
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LIQUID-PHASE PHOTOIONIZATION DETECTOR FOR LIQUID CHROMATOGRAPHY (HPLC).
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Identifier
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AAI8401927
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identifier
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8401927
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Creator
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DHINGRA, BHIM SEN.
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Contributor
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David C. Locke | Arthur D. Baker
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Date
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1983
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Analytical
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Abstract
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A wide variety of detection schemes have been developed in pursuance of the development of a universal, sensitive detector for high pressure liquid chromatography (HPLC). Although useful, none of these detectors approach the sensitivity of the flame ionization detector (FID) for gas chromatography (GC).;In the present work a direct liquid phase photoionization detector with picogram sensitivity to polycyclic aromatic hydrocarbons in normal phase chromatography is described. This detector is based on the selective photoionization of the eluent. Photoionization in liquids is a more complex phenomenon than that in gases. In liquids (pi)-electron photocurrents are observed for incident photon energies 2-4 eV less than the vacuum IP values. In liquids, it is also possible to have secondary reactions in addition to the simple solvation of the product ions.;In this detector the ionizing UV-light is generated by a microwave excited Xe-lamp. This lamp emits a continuum of radiation with a short wavelength cutoff at 1600 A (7.81 eV), which provides sufficient energy to ionize many solutes but not to ionize appreciably the hexane-2-propanol eluent. The amplified photocurrents are linear with concentration over at least 6 orders of magnitude. The response of the detector is reproducible. The effective ionization efficiencies are of the order of 10('-8). Both positive and negative ion currents are found to be identical. Although the exact nature of the anionic and cationic species collected is not clear, the mobility values indicate they are radical ions. No signal is observed for low molecular weight phenols or chlorinated compounds in hexane-2-propanol but these compounds gave small signals in polar solvents such as ethyl ether, tetrahydrofuran. A mixture prepared from known concentrations of commercially obtained polycyclic aromatic hydrocarbons was analysed. An attempt to detect the compounds using a phase-sensitive detector was unsuccessful.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Chemistry
